Increased nuchal translucency thickness at 10-14 weeks of gestation as a predictor of severe twin-to-twin transfusion syndrome.

The study examines a possible association between increased nuchal translucency thickness at 10-14 weeks of gestation in monochorionic twin pregnancies and the subsequent development of severe twin-to-twin transfusion syndrome (TTS). In 132 monochorionic twin pregnancies, including 16 that developed severe TTS at 15-22 weeks of gestation and 116 that did not develop TTS, crown-rump length, nuchal translucency thickness and fetal heart rate were measured at 10-14 weeks. In those that developed severe TTS, the prevalence of nuchal translucency thickness above the 95th centile of the normal range and the intertwin difference in nuchal translucency thickness and fetal heart rate were significantly higher than in the non-TTS group; there were no significant differences between the groups in the inter-twin difference in crown-rump length. For fetal nuchal translucency above the 95th centile, the positive and negative predictive values for the development of TTS were 38% and 91%, respectively; the likelihood ratios of nuchal translucency above or below the 95th centile for the development of severe TTS were 4.4 (1.8-9.7) and 0.7 (0.4-0.9), respectively. These findings demonstrate that the underlying hemodynamic changes associated with TTS may manifest as increased fetal nuchal translucency thickness at 10-14 weeks of gestation.